Windows are one of the primary sources of heat loss in architectural structures. One way to reduce such heat loss is by providing vacuum insulating glass units. Conventional vacuum insulating glass (VIG) units include two spaced apart glass panes that enclose an evacuated or low pressure space. The low pressure in the between-pane space reduces or eliminates convective heat transfer between the glass panes.
VIG units can be fabricated in different configurations that allow the glass panes to be spaced apart while maintaining a vacuum in the between-pane space. In one configuration, a spacer is placed between the two glass panes. The spacer forms a seal between the two glass panes to enclose the between-pane space and maintain a vacuum therein. Such an arrangement provides structural stability, but a common issue with this configuration is a gradual loss of vacuum over time due to permeability of the seals. With a conventional VIG unit, when vacuum is lost, air enters the between-pane space and can bring with it moisture. This reduces the insulating effect provided by an evacuated or low pressure space.
In other configurations, instead of using a spacer, the edges of the two glass panes are fused together to form a seal. In this arrangement, an array of small metal pillars or cylinders is typically placed between the two panes to keep them from collapsing due to the vacuum in the between-pane space. This configuration is initially more air-tight than VIG units sealed with spacers. This type of arrangement, however, may provide less structural stability. For example, the fused edges of the glass panes tend to have little, if any, flexibility. As a result, the edges of these units tend to be somewhat brittle and thus more fragile than would be ideal.
It would be desirable to provide a VIG unit that effectively maintains good thermal insulating properties in addition to being structurally robust.